A mix that comes from different cultures produces always good results, and there is another prove: the school.
In Berlin there are more than 350 public schools, and Sandra Scheeres (responsible of quality of education) said that after about 5 years of investigation she is sure: the best schools are those where the students are a mix of cultures, sons of migrants.
In these schools the quality of education, learning ability and interaction between students and teachers is better than schools where you can find just germans.
Of course the fact they come from a different cutlures and societies create circumstances where they have to be more elastic, and open. And this is the best start point for a school!
Especially in a city like Berlin, where multiculturalism is so common, this should be the best way to prepare the next generations of men and women for the world and the Europe we are building.